RE: [media-types] Update to media type "application/ttml+xml"

From: Michael Dolan <mdolan@newtbt.com> · Date: Tue, 21 Jun 2016 09:20:45 -0700

Hi Paul-

Thanks. FYI, we're mainly focused on the addition of the codecs parameter.
The rest of the text remains unchanged from the prior registration in TTML1.

Maybe one of the tools vendors on the reflector knows of specific details to
propose?

                Mike

                (Note editor)

From: Paul Libbrecht [mailto:paul@hoplahup.net] 
Sent: Friday, June 17, 2016 9:09 AM
To: Philippe Le Hegaret <plh@w3.org>
Cc: media-types@iana.org; Timed Text Working Group <public-tt@w3.org>;
'Michael Dolan' <mike@dolan.tv>
Subject: Re: [media-types] Update to media type "application/ttml+xml"

Dear Philippe,

I could not find a complete information but it looks like TTML is a format
that could be contained in a clipboard. E.g. when transporting a (piece of
a) transcript from one document to another. Could I, thus, suggest that you
add below the Macintosh File type and such extra information two fields:
- Windows clipboard flavour:
- MacOS uniform type identifier:
In order to find the right clipboard type names, a little bit of research
should be done on the existing practice.
Which tools exist out there which can accept or produce TTML?

thanks in advance.

Paul

 <mailto:plh@w3.org> Philippe Le Hegaret

16 June 2016 at 16:16

The W3C Timed Text Working Group would like to update the media type
"application/ttml+xml" as follows. Comments are welcome. 

It updates the media type, "application/ttml+xml" to add a new parameter,
codecs. All other provisions of the media type specification remain the
same. This supercedes the initial registration information in TTML 1.0
Second Edition. 

Text copied below but see also the original text at: 
 https://www.w3.org/TR/2016/NOTE-ttml-profile-registry-20160510/#mediatype 

[[ 

Type name: 

    application 
Subtype name: 

    ttml+xml 
Required parameters: 

    None. 
Optional parameters: 

    charset 

        If specified, the charset parameter must match the XML encoding
declaration, or if absent, the actual encoding. See also Encoding
Considerations below. 
    profile 

        The document profile of a TTMLDocument Instance may be specified
using an optional profile parameter, which, if specified, the value of which
must adhere to the syntax and semantics of ttp:profile parameter defined by
TTML 1.0 Second Edition, Section 6.2.8 ttp:profile of the published
specification. 

    codecs 

        The optional codecs parameter provides a short form version of the
profile parameter with multiple-profile combinatorial capability. If a short
(4-character) form of a profile is registered in the TTML Profile Registry,
it is recommended that this codecs parameter be used and not the profile
parameter. The nominal value of this parameter is a single 4 character code
from the registry. 

        Additionally, applications using the entries in the registry are
encouraged to adopt the following combination syntax: 

        Employ two combination operators, '+' (AND) and '|' (OR), which may
be used to specify, respectively, that multiple processor profiles apply
(simultaneously) or that any processor profile of a list of profiles may
apply individually. If both operators are used in a codecs value, then the
'+' operator has precedence. 

        The example: "A+B|C+D|E" states that a TTML processor that
implements any one of A+B or C+D or E processor profiles satisfies, at first
order, the requirements to fetch and begin decode/processing of a TTML
document, where X+Y means that both X and Y processor profiles must be
supported, and X|Y means that either X or Y processor profile must be
supported. 

        For more information about processor profile combination, see TTML2
Profile Combination. 

Encoding considerations: 

    Same for application/xml, except constrained to either UTF-8 or UTF-16.
See IETF RFC 3023, XML Media Types, Section 3.2. For the purpose of filling
out the IANA Application for Media Type
(http://www.iana.org/cgi-bin/mediatypes.pl), the value binary applies. 
Security considerations: 

    As with other XML types and as noted in IETF RFC 3023, XML Media Types,
Section 10, repeated expansion of maliciously constructed XML entities can
be used to consume large amounts of memory, which may cause XML processors
in constrained environments to fail. 

    In addition, because of the extensibility features for TTML and of XML
in general, it is possible that "application/ttml+xml" may describe content
that has security implications beyond those described here. However, TTML
does not provide for any sort of active or executable content, and if the
processor follows only the normative semantics of the published
specification, this content will be outside TTML namespaces and may be
ignored. Only in the case where the processor recognizes and processes the
additional content, or where further processing of that content is
dispatched to other processors, would security issues potentially arise. And
in that case, they would fall outside the domain of this registration
document. 

    Although not prohibited, there are no expectations that XML signatures
or encryption would normally be employed. 
Interoperability considerations: 

    The published specification describes processing semantics that dictate
behavior that must be followed when dealing with, among other things,
unrecognized elements and attributes, both in TTML namespaces and in other
namespaces. 

    Because TTML is extensible, conformant "application/ttml+xml" processors
may expect (and enforce) that content received is well-formed XML, but it
cannot be guaranteed that the content is valid to a particular DTD or Schema
or that the processor will recognize all of the elements and attributes in
the document. 
Published specification: 

    This media type registration is extracted from the TTML Profile
Registry. 
Applications that use this media type: 

    TTML is used in the television industry for the purpose of authoring,
transcoding and exchanging timed text information and for delivering
captions, subtitles, and other metadata for television material repurposed
for the Web or, more generally, the Internet. 

    There is partial and full support of TTML in components used by several
Web browsers plugins, and in a number of caption authoring tools. 
Additional information: 

    Magic number(s): 
    File extension(s): 

        .ttml 
    Macintosh file type code(s): 

        "TTML" 
    Fragment identifiers: 

        For documents labeled as application/ttml+xml, the fragment
identifier notation is intended to be used with xml:id attributes, as
described in section 7.2.1 of the Timed Text Markup Language 1 (TTML1)
specification. 

Person & email address to contact for further information: 

    Timed Text Working Group (public-tt@w3.org <mailto:public-tt@w3.org> ) 
Intended usage: 

    COMMON 
Restrictions on usage: 

    None 
Author: 

    The published specification is a work product of the World Wide Web
Consortium's Timed Text (TT) Working Group. 
Change controller: 

    The W3C has change control over this specification. 
]] 
https://www.w3.org/TR/2016/NOTE-ttml-profile-registry-20160510/#mediatype 

Thank you, 

Philippe 

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